On 6/4/2009 11:29 AM josef.p...@gmail.com apparently wrote: > intersect1d is the intersection between sets (which are stored as > arrays), just like in the mathematical definition the two sets only > have unique elements
Hmmm. OK, I see you and Robert believe this. But it does not match the documentation. But indeed, I see that the documentation is incorrect. E.g., >>> np.intersect1d([1,1,2,3,3,4],[1,4]) array([1, 1, 3, 4]) Is this a bug or a documentation bug? > intersect1d_nu is the intersection between two arrays which can have > repeated elements. The result is a set, i.e. unique elements, stored > as an array > same for setmember1d, setmember1d_nu I cannot understand this. Following your proposed reasoning, I expect a[setmember1d_nu(a,b)] to return the same as intersect1d_nu(a, b). It does not. > so postfix `_nu` only means that this function also works > if the two arrays are not really sets But that just begs the question: what does 'works' mean? See my previous comment (above). > intersect1d should throw a domain error if you give it arrays with > non-unique elements, which is not done for speed reasons *If* intersect1d behaved *exactly* as documented, the example intersect1d(a, np.unique(b)) shows that the documented behavior can be useful. And indeed, this would be the match to a[setmember1d_nu(a,b)] Cheers, Alan Isaac _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
